Vehicle bumper system

ABSTRACT

A vehicle bumper system defined principally by outboard and inboard elongate beams which project transversely across the vehicle. The ends of the front and rear beams are joined by connecting points which function as energy-absorbing fulcrums or hinges, with the remainder of the front and rear beams initially being free of direct structural connection. The front beam is outwardly curved so that the center portions of the front and rear beams define a gap therebetween. The rear beam has connections to the vehicle at two points spaced transversely inwardly from the end connections, which connections define inboard fulcrum or hinge points. The front and rear beams are each formed as elongate monolithic structures, such as of high strength steel, and have configurations which enable them to nest one within the other in the longitudinal direction of the vehicle.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority under 35 USC §119 (e) ofcopending provisional application Serial No. 60/350,725 filed Jan. 22,2002, the entire disclosure of which is herein incorporated byreference.

FIELD OF THE INVENTION

[0002] This invention relates to a bumper system for a vehicle and, morespecifically, to an improved bumper system which can be constructed ofsmall package size while providing high energy absorption capability.

BACKGROUND OF THE INVENTION

[0003] Bumpers are used on motor vehicles to absorb low level impactforces and to limit the amount of damage sustained to the vehicle bodyduring high level impacts. In an attempt to achieve this objective, manyof the known bumper systems have necessarily resulted in arrangementsinvolving an undesirably large size or space requirement, and inaddition have resulted in undesired structural complexity and cost. Inaddition, it is believed that most such bumper systems have failed toprovide for maximum energy absorption resulting from an impact,particularly in relationship to the overall size, weight, cost andprotectability of the known bumper systems.

[0004] Conventional design practice is to provide a bumper system havinga single armature (i.e., a simple beam) which, when impacted, absorbsenergy by permitting buckling (i.e., plastic deformation) at locationsconcentrated at the vehicle centerline of the beam and at the locationswhere the beam mounts to the vehicle. This arrangement of the simplebeam, however, provides an inefficient energy absorbing capability, andhence the bumper system is conventionally provided with separate energyabsorbers such as struts, springs or foam members which cooperate withthe beam. This conventional design is thus complex and requiressignificant space to package it on a vehicle, and generally results inan inefficient use of material and often results in a system havingsignificant weight.

[0005] The present invention relates to an improved bumper system for avehicle which attempts to improve on conventional prior artconstructions by providing a multiple-beam bumper system which, inconjunction with the connections to the vehicle, define multiple fulcrumpoints so that the bumper system is effectively defined by multiplebeams which permit more effective absorption of energy, as caused by animpact against the bumper, due to relative movements of the beams andthe permissible plastic energy-absorbing deformations which occur withinthe bumper system.

[0006] The bumper system of the present invention, as aforesaid, inaddition to permitting more effective dissipation of energy within thebumper system prior to the ending of an external impact event, is alsobelieved to represent a bumper system solution which can be more readilyand less expensively manufactured and can be incorporated into a smallerpackage depth by permitting more energy to be dissipated per unitdistance of impact intrusion.

[0007] In the improved vehicle bumper system of this invention, thesystem is defined principally by outboard (i.e. front) and inboard (i.e.rear) elongate beams which project transversely across the vehicle. Theends of the front and rear beams are joined by connecting points whichfunction as energy-absorbing fulcrums or hinges, with the remainder ofthe front and rear beams initially being free of direct structuralconnection. The front beam is preferably of an outwardly curvedconfiguration so that the center portions of the front and rear beamsdefine a horizontal space or gap therebetween. The rear beam defines thestructural connection to the vehicle, and in particular the rear beam attwo points disposed on opposite sides of the vehicle longitudinalcenterline, and spaced transversely inwardly from the end connections,is joined to mounting elements or rails on the vehicle by connectionswhich define inboard fulcrum or hinge points. The front and rear beamsare each preferably formed as elongate monolithic structures, such as ofhigh strength steel, and have configurations which enable them to nestone within the other in the longitudinal direction of the vehicle. Forexample, one of the beams is preferably of a C-shaped cross section, andthe other beam is of a compatible C-shaped or hollow rectangularconfiguration to enable the two beams to at least partially nest. Thetwo beams, in the nondeformed condition, have the end parts thereofnested together to define the outboard connections thereat. An externalimpact against the front beam can effect rearward deflection thereof andtransmission of energy along the front beam to the outboard connections,which in turn effect energy absorption at the end beam portions of therear beam which project between the inboard and outboard connections.This also causes the center portion of the rear beam to deflectforwardly toward the front beam to effect additional energy absorption,with the front and rear beams being moved toward one another for moreeffective nesting engagement so that the two beams ultimately act as oneso as to permit additional absorption of the impact energy. Additionalconnecting blocks can be provided for cooperation between the front andrear beams if desired.

[0008] In the improved bumper system of the present invention, asaforesaid, the front and rear beams and their connections to one anotherat the outboard ends, and the connection of solely the rear beam to thevehicle at the inboard connection points, effectively define a kinematicstructure having four connection points which function similar tofulcrums in that they permit energy-absorbing relative motion betweenthe front and rear beams, and between the rear beam and the vehicleframe, with the energy absorption being in various stages as the impactevent progresses. Further, the four connection points effectively causethe front and rear beams to define a four-beam system, with the rearbeam having three beam portions due to the pairs of inboard and outboardconnection points. This in addition enables the center beam portion ofthe rear beam to undergo outward bowing or deflection (i.e. away fromthe vehicle) toward the front beam during an impact event so as toimprove the energy-absorbing capabilities while at the same timeminimizing or delaying the impact of the bumper against the remainder ofthe vehicle.

[0009] Other objects and purposes of the improved bumper systemaccording to the present invention will be apparent to persons familiarwith systems of this general type upon reading the followingspecification and inspecting the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a perspective view of an improved bumper assemblyaccording to the present invention.

[0011]FIG. 2 is a diagrammatic plan view illustrating the inventivebumper system and its connection to a vehicle.

[0012]FIG. 3 is an enlarged cross-sectional view taken along line 3-3 inFIG. 2 and showing the cross section of the front and rear beams.

[0013]FIG. 4 is a view similar to FIG. 3 but illustrating a variation inthe beam cross sections.

[0014]FIG. 5 is a further view similar to FIG. 3 and illustrating afurther variation of the beam cross sections.

[0015]FIG. 6 is a perspective view similar to FIG. 1 but illustrating abumper system having contact blocks associated with the rear beam.

[0016]FIG. 7 is an enlarged central cross-sectional view of the bumpersystem of FIG. 6.

[0017] Certain terminology will be used in the following descriptionsfor convenience in reference only, and will not be limiting. Forexample, the words “upwardly”, “downwardly”, “rightwardly” and“leftwardly” will refer to directions in the drawings to which referenceis made. The word “front” will refer to a direction which faces awayfrom the vehicle end, namely upwardly in FIG. 2, and the word “rear”will refer to the opposite direction. The words “inwardly” and“outwardly” will refer to directions toward and away from, respectively,the geometric center of the bumper system and designated parts thereof.Said terminology will include the words specifically mentioned,derivatives thereof, and words of similar import.

DETAILED DESCRIPTION

[0018] Referring to FIGS. 1 and 2, there is illustrated an improvedvehicle bumper system 11 according to the present invention. The bumperassembly 11 is adapted to be mounted on the front and/or rearward end ofa vehicle, the frame or basic structure of which is diagrammaticallyindicated at 12 in FIG. 2.

[0019] The bumper assembly 11 is made up principally of two mainelongate beams or armatures, namely a rigid front or outboard beam 13and a rigid rear or inboard beam 14, the latter being interposed in thespace between the front beam 13 and the vehicle. The beams 13 and 14project generally horizontally and transversely with respect to thelongitudinal direction of the vehicle, namely the typical direction ofvehicle movement, and in plan view as illustrated in FIG. 2 aresymmetrical with respective to the longitudinal centerline 15 of thevehicle.

[0020] The front beam 13, adjacent opposite free ends thereof, has endportions 16 which are joined by end connections 17 to respective endportions 18 defined at opposite free ends of the rear beam 14. The endconnection 17 defines a relatively rigid connection between the ends ofbeams 13 and 14 so that these beams can relatively rotate or angularlydisplace at this end connection only in response to application of asignificant force-created moment which provides energy absorption andtransmission as the bumper assembly deflects and deforms in response toan external impact against the front beam 13. The end connectors 17 thusfunction as energy-absorbing vertical fulcrums which will typicallypermit relative angular displacement between the beams in response toapplication of sufficient energy as to cause plastic energy-absorbingdeformation. The end connections 17 provided between the ends of thefront and rear beams is the principal structural connection betweenthese elements.

[0021] The rear beam 14 in turn provides the principal structuralconnection to the vehicle, such as to a pair of frame or mountingmembers (i.e. rails) 23 which are associated with the end of the vehiclefor connection to the bumper system. The vehicle mounting members 23 aredisposed spaced from and typically symmetrically on opposite sides ofthe centerline 15, and connect directly to the rear beam 14 byconnections 24 which preferably function as vertical fulcrums or hinges.

[0022] The pair of connections 24, herein referred to as inboardconnections, are spaced inwardly relative to the end or outboardconnections 17, whereby the connections 24 have no direct contact orengagement with the front beam 13 when the bumper assembly is in anon-deformed condition. This disposition of the inboard and outboardconnections 24 and 17, respectively, causes the rear beam 14 to beeffectively divided into three beam portions, namely an elongate centerportion 21 which extends between the connection points 24, and a pair ofend beam portions 19 which extends between the inboard connections 24and the adjacent outboard connections 17.

[0023] The front beam 13, in a generally horizontal plane, is preferablyprovided with an outwardly curved or arcuate shaped configurationthroughout the lengthwise extent thereof so that it bows or curvesoutwardly in the longitudinal direction of the vehicle. The rear beam 13may be straight as illustrated, or may be provided with a forwardarcuate or outwardly bowed configuration if desired, although thearcuate shape of the inboard or rear beam 14 would be less than that ofthe front or outer beam 13. The configuration of the beams 13 and 14when in the assembled state, and prior to being subjected to an externalimpact, is such that the center portion of the front beam 13 is spacedforwardly from the center portion 21 of the rear beam 14 so as to definea horizontal gap or space 22 therebetween.

[0024] The front and rear beams 13 and 14 are preferably provided withthree-dimensional cross sections which, at least in part, involve aC-shaped configuration so as to permit the front and rear beams toeffectively nest one within the other, which nesting relationship existsinitially only at the ends 16 and 18.

[0025] More specifically, as illustrated by FIG. 3, the front beam 13 inone preferred embodiment of the invention has a generally C-shaped crosssection which opens rearwardly and is defined by a upright front wall 26which, at upper and lower ends, joins to rearwardly projecting top andbottom walls or legs 27. The rear beam 14 is of a similarrearwardly-opening C-shaped cross section defined by an upright frontwall 28 which at upper and lower edges is joined to rearwardlyprojecting top and bottom walls or legs 29. The overall height of therear beam 14 is selected so as to permit it to move into the interior of(i.e., nest within) the front beam 13, the latter having sufficientspacing between the inside surfaces of the top and bottom walls 27 so asto permit the rear beam 14 to be positioned therebetween. This nestingrelationship enables the ends 16 and 18 to nest together and permit thefront and rear beams to be joined at the connections 17, whichconnections will typically exist between the overlapping top and bottomwalls 27 and 29. The center portions of the beams, however, will bespaced apart as illustrated in FIG. 2, and as illustrated in FIG. 3wherein the front beam 13 is spaced forwardly from the rear beam 14.

[0026] If desired, the overall structural properties of the rear beam 14can be further enhanced by forming same as a closed tube of generallyrectangular cross section. This is achieved in the illustratedembodiment by closing off the C-shaped rear beam by means of a back wall25, the latter having flanges which can be suitably fixed, as bywelding, to the top and bottom walls 29. Alternately, the rectangularprofile of the rear member 14 in FIG. 3 can be formed using otherstructural techniques, such as by roll forming the rectangular tube andthen longitudinally seam welding same.

[0027] As a modification which effectively is a reversal of thearrangement shown in FIG. 3, the front and rear beams can be constructedas illustrated in FIG. 4. In this variation, the front beam 13′ has agenerally rectangular tubular cross section defined by front and rearwalls 31 and 32 respectively, joined by top and bottom walls 33, and therear beam 14′ is a forwardly opening C-shaped cross section defined byan upright rear wall 34 joined to forwardly projecting top and bottomwalls 35. The interior of the C-shaped rear beam 14 is sized so as topermit the tubular front beam 13′ to nest within the rear beam 14′.

[0028] A still further variation of the cross section of the front andrear beams is illustrated in FIG. 5. In this variation the front beam13″ and rear beam 14″ are both of a hollow tubular cross sectionconfigured to nest one within the other. More specifically, the frontbeam 13″ is a hollow C-shaped member which opens rearwardly and isdefined by spaced outer and inner upright front walls 41 and 42respectively, and the front beam has rearwardly projectingchannel-shaped hollow legs defined by outer top and bottom walls 43which join to the outer front wall 41, and inner top and bottom walls 44which join to the inner front wall 42, with the hollow legs being closedoff at rearward ends by rear walls 45. The rear beam 14″ is of arectangular tubular cross section defined by upright front and rearwalls 47 and 48, respectively, rigidly joined by top and bottom walls49. The height of the rear beam 14″ is such as to permit it to nestwithin the interior of the C-shaped front beam 13″, generally in therecess defined between the upper and lower walls 44.

[0029] The front and rear beams 13 and 14, including the variationssuggested by FIGS. 3-5, are preferably individually constructed asone-piece monolithic elongate metal members, preferably high strengthsteel of at least 100 ksi yield strength, with the beams preferablybeing roll formed so as to provide the beams with desirable shape andstrength properties. The front and rear beams 13 and 14 are assembledtogether, such as through the outboard connectors 17, such that each ofthe beams 13 and 14 in the assembled condition is in its preformed andhence non-stressed shape. As to the fulcrum connectors 17, they willtypically be a rigid or semi-rigid connector which will provide orpermit a springlike connection between the front and rear beams adjacentthe free ends thereof so that, upon application of an impact forceagainst the front beam, the front beam can deflect inwardly andsimultaneously effect transmission of impact energy lengthwise along thebeam into the outboard connectors 17 associated with opposite sides ofthe bumper arrangement. These connectors 17, such as elastically and/orplastically deformable springlike hinges, permit appropriate deflectionand movement at the connector so as to absorb additional energy, and atthe same time the end beam portions 19 associated with the rear beam 14can elastically and plastically deflect or deform rearwardly about theinboard connection points 24. This latter deflection will typically beaccompanied by forward deflection or bowing of the rear center beamportion 21 toward the center portion of the front beam 13, with thisforward deflection of the center rear beam portion 21 effectingabsorption of additional impact energy.

[0030] As the impact energy continues to be applied to and absorbed inthe bumper system, the opposed center portions of the front and rearbeams both move, and effectively move in opposite directions toward oneanother until the center portions effectively nest one within the other.At this stage the front and rear beams thus effectively function as asingle beam and are effective for absorbing additional impact energy asthe nested center portions of the front and rear beams are deflectedrearwardly.

[0031] The overall bumper assembly and specifically the constructionemploying front and rear beams coupled principally by the two outboardconnection points 17, and the coupling of the rear bumper member 14 tothe vehicle through the two inboard connection points 24, thuseffectively provides a four-point kinematic action which enables theimpact energy to be progressively absorbed as a result of movement anddeformation of the different parts of the front and rear beams inresponse to an external impact against the front beam. At the same time,the fact that the rear beam is initially deflected outwardly away fromthe vehicle into engagement with the front beam, prior to its thereafterbeing effectively coupled with the front beam and deflected inwardlytoward the vehicle for further energy absorption, is believed to permita higher quantity of energy to be effectively absorbed within the bumpersystem prior to impact of the bumper against the vehicle, with theoverall bumper system still occupying only a minimum space envelope whenmounted on the vehicle.

[0032] Considering in greater detail the energy-absorbing endconnections 17 which join the ends of the outboard beam 13 to therespective ends of the inboard beam 14, this connection 17 preferablyprovides significant rotational resistance between the connected ends ofthe beams 13 and 14 such that a significant force-created moment isrequired to effect angular displacement of the connected ends of thebeams 13 and 14, which in turn results in significant absorption ofimpact energy as imposed on the bumper system. This energy-absorbing endconnection 17 hence may absorb some energy due to elastic deformation ofthe material associated with the beams or the end connection, but moresignificantly causes energy absorption due to plastic deformation of thematerial.

[0033] The end connection 17, in a typical and practical construction ofthe bumper assembly, may be created by a welded connection between thebeams 13 and 14 adjacent the free ends thereof. Such welded connectionis preferably defined by a horizontally elongated weld, and morepreferably a vertically-spaced pair of horizontally-elongated weldswhich connect the ends of the two beams 13 and 14 together. For example,with the arrangement illustrated by FIGS. 1-3, a firsthorizontally-elongate weld can be provided at the cooperating ends ofthe beams between the top wall of the rear beam and the top leg of thefront beam where these beams nest together, such weld beingdiagramatically indicated at 20 in FIG. 2, and a similarhorizontally-elongate weld can be provided between the bottom wall ofthe rear beam and the lower leg of the front beam. Such weldarrangement, and the end connection defined thereby, hence preventsrelative horizontal translation between the ends of the beams due toimposition of an external impact against the bumper system, and at thesame time may permit limited angular displacement between the ends ofthe connected beams due principally to plastic deformation of the beammaterial in the vicinity of the end connections, which plasticdeformation is effective for absorbing at least some of the externalimpact energy while permitting other external impact energy to betransmitted through the connection to the inboard beam.

[0034] In place of an end connection employing welds as described above,the end connection 17 may involve some type of mechanical interlockbetween the cooperating ends of the beams, such as a tab on one beamprojecting into a slot or groove on the other beam, so as to function ingenerally the same manner as described above. Further, the mechanicalinterlock may involve some type of connecting pin or coupling member,such as a square or non-round pin or a press or interference fit pin,which imposes substantial resistance against relative rotation betweenthe connected ends of the beams 13 and 14, which connector hence resistsrelative translation and/or rotation between the connected ends butpermits energy absorption at the connection due to plastic deformationof material associated with the end parts of the beams and/or theconnector.

[0035] As a still further alternative, the end connector 17 joining theend parts of the beams 13 and 14 may comprise a heavy-duty spring shapedand configured to provide generally the same energy-absorbing functionas described above. For example, the spring ends can be anchored orfixed to the connected end parts of the beams.

[0036] Regarding the connections 24 between the inboard beam 14 and theframe rails 22, these connections will preferably be initially designedso as to optimize the ability of the inner beam to transmit energy fromthe end parts to the center part thereof while at the same timepermitting the inner beam to effectively absorb impact energy at boththe end or outboard parts as well as in the center part thereof. Theconnection 24 will preferably provide resistance against at leasthorizontal translation or horizontal rotation so as to permit at leastsome of the energy transmitted to the outboard parts of the inboard beam14 to be transmitted along the beam into the center part thereof. Theconnection 24 may comprise vertical hinge pins which will hence permitlimited horizontal rotation but prevent horizontal translation.

[0037] As a further and preferred construction in terms of simplicity ofvehicle manufacture and assembly, the connection 24 may involve a weldedconnection between the inboard beam 21 and the rail 22, which weldedconnection may be similar to spot welds at the points 24, or whichwelded connection may be defined by a vertically elongate weld betweenbeam 21 and rail 22 which will be effective in preventing relativetranslation movement but at the same time may permit plastic deformationin the beam at the weld similar to a horizontal flexing movement due tothe plastic deformation of the material in the vicinity of the weld.Such vertically elongate weld is diagrammatically shown at 30 in FIG. 2.

[0038] Referring to FIG. 2, there is illustrated a variation of thebumper assembly 11 which permits some of the impact forces applied tothe outer beam 13 to be short circuited and communicated directly to therear beam 14 without passing through the end connectors 17. In thisvariation, a force communicator structure 53, as indicated by dottedlines in FIG. 2, can be disposed within the gap 22 for connectionbetween the front and rear beams at locations spaced inboard from theend connectors 17. The communicator member 53 will typically besandwiched between the front and rear beams 13 and 14 to provide apartial force-transmitting short circuit from the front beam 13 throughthe member 53 to the rear beam 14, whereby some impact force and energyhence will be transmitted through the communication member 53, and otherof the impact energy will transmit along the beam 13 to the endconnectors 17 for application to the ends of the rear beam 14 in thesame manner as described above.

[0039] The communicator member 53 may be formed as one or moredeformable foam or plastic or metal members for connection directlybetween the front and rear beams and, for example, for connectiondirectly between the center beam portions of the front and rear beams.The communicator 53 will typically be engaged with the rear beam 14 atone or more locations positioned inwardly from the inboard connectors24. The foam connector member 53 may be of a crescent shape so as tooccupy substantially the entire gap between the beams 13 and 14. It willbe appreciated that the communication member 53 will permit only part ofthe impact energy to be transmitted therethrough, and that the geometryof the bumper assembly will be effective with respect to the remainingimpact energy so that the bumper assembly functions in the same manneras if the communicator 53 was not present, such as described above.

[0040] Referring now to FIGS. 6 and 7, there is illustrated a modifiedbumper assembly wherein, in this arrangement, the bumper assembly isdefined by a front beam 13″ and a rear beam 14″ which are operativelycoupled and mounted in the same manner as illustrated by FIG. 2, andgenerally have cross sections similar to that illustrated by FIG. 5. Inthis variation, however, the rear beam 14″ has communication or contactblocks or members 51 fixedly mounted thereon in the vicinity of thecenter of the beam (i.e., substantially at or adjacent the longitudinalcenterline 15), and these communication blocks 51 are fixedly secured toand respectively project upwardly and downwardly from the upper andlower walls of the rear beam at a location close to the front wall. Withthis arrangement, the communication blocks 51 are oriented such that,upon relative deflection of the center portions of the front and rearbeams so that they relatively move toward one another into a nestingposition, the communicator blocks 51 on the rear beam will contact therear wall associated with the legs of the front beam, prior to the rearbeam fully nesting within the front beam, thereby effectively providinga solid connection between the center portions of the front and rearbeams. At this stage the front and rear beams hence effectively functionas a single beam so as to effect continued absorption of energyassociated with the impact event. This latter stage, wherein thecommunication blocks 51 contact the rear wall of the front beam, requirethat the bumper assembly undergo the various energy-absorbing deflectingand deformation stages described above, namely the initial deformationof the front beam followed by deformation of the rear beam and outwardbowing of the center portion thereof, so as to cause the communicationblocks 51 to contact the front beam so that the two beams thereaftereffectively act in unison with respect to further energy absorption.

[0041] With the improved bumper assembly of the present invention, theoutboard connectors 17 can be effectively tuned during the initialdesign thereof so as to optimize the moment and hence energy appliedfrom the front beam to the rear beam in accordance with the overallgeometry of the bumper system, which tuning can be accomplished by theoverall initial design of the connector 17 with respect to the degree ofrigidity and elasticity incorporated therein. In addition, the C-shapedand hollow cross sections contemplated for use in forming the front andrear beams also permit the desired absorption of energy due to thedeformation of the beam cross-sections, and these configurationstogether with the coupled relationship of the inner and outer beams andthe four-point kinematic connections defined by the connectors 17 and 24hence maximize the energy absorption capability of the bumper system,and hence the energy absorbing capability thereof prior to the bumperdeforming into contact with the end of the vehicle.

[0042] While the bumper system in the illustrated embodiments has theends of the front and rear beams connected at the connectors 17, it willbe recognized that one of these beams may have ends which overhang orproject outwardly beyond the connectors 17 without detracting from thefunction of the bumper system as summarized herein.

[0043] As is conventional, the front beam 13 can be provided with asuitable covering or cap, such as of a plastic material or the like, soas to provide the bumper with the desired styling and color consistentwith the desired visual aspects of the vehicle.

[0044] Although a particular preferred embodiment of the invention hasbeen disclosed in detail for illustrative purposes, it will berecognized that variations or modifications of the disclosed apparatus,including the rearrangement of parts, lie within the scope of thepresent invention.

What is claimed is:
 1. A bumper system for attachment to an end of avehicle, comprising: a first horizontally elongate beam positioned toextend transversely relative to a traveling direction of the vehicle; asecond horizontally elongate beam positioned adjacent but inwardly ofsaid first beam and extending transversely relative to said travelingdirection; said first beam having an elongate center beam part whichextends between and joins to a pair of first end parts as definedadjacent opposite ends of said first beam, said second beam havingsecond end parts adjacent opposite free ends thereof, said second endparts being disposed adjacent said first end parts respectively; aconnecting structure joining each said first end part to the adjacentsecond end part, said connecting structures defining a pair of firstenergy-absorbing fulcrum-like connections between said first and secondbeams adjacent opposite ends thereof; each of said first and secondbeams being of high strength steel and being substantially nonstressedwhen joined together by said connecting structures; said second beambeing joined to mounting parts of said vehicle by a pair of sidewardlyspaced connection structures which define a pair of second fulcrum-likeconnections between said vehicle and said second beam, said secondfulcrum-like connections being spaced inwardly from said firstfulcrum-like connections so that said second beam includes an elongatecenter beam portion which extends between said second fulcrum-likeconnections and a pair of end beam portions which each extends from oneof said second fulcrum-like connections to the adjacent firstfulcrum-like connection; said first beam being preshaped so that saidcenter beam part is bowed horizontally forwardly from said first endparts so as to be spaced forwardly from but generally horizontallyaligned with the center beam portion of said second beam; each of saidfirst and second beams having at least a horizontally oriented C-shapedcross section, the C-shaped cross section of one said beam openingtoward said other beam. whereby an external impact against said firstbeam transmits force to said pair of first fulcrum-like connections toeffect elastic deflection of said end beam portions and forward bowingof said center beam portion of said second beam.
 2. A bumper systemaccording to claim 1, wherein said center beam part and said center beamportion can relatively move into at least partial nested engagement withone another in response to an external impact on said first beam.
 3. Abumper system according to claim 1, wherein one of said first and secondbeams has a hollow rectangular cross section which, upon external impactagainst said first beam, can relatively move into nested engagementwithin the C-shaped cross section of the other of said first and secondbeams.
 4. A bumper system according to claim 1, wherein each said firstfulcrum-like connection comprises a rigid but deformable fulcrumstructure for permitting energy-absorbing relative movement between thejoined first and second end parts of said first and second beams.
 5. Abumper system according to claim 1, wherein the center beam part and thecenter beam portion are initially free of direct rigid connectiontherebetween to permit relative engaging movement therebetween inresponse to external impact on said first beam.
 6. A bumper systemaccording to claim 1, wherein a deformable energizing member isconnected directly between the center beam part of said first beam andthe center beam portion of said second beam to permit partial energyabsorption and partial transference of force to the center beam portionof said second beam upon imposition of an external impact against saidfirst beam.
 7. A bumper system according to claim 6, wherein saiddeformable energizing member includes a blocklike foam member or afoamed plastic member.
 8. A bumper system according to claim 2, whereinone of said center beam part and said center beam portion has upper andlower communication members fixed thereto and positioned for contactingengagement with the other of said center beam part and said center beamportion when said center beam part and said center beam portion movetoward one another in response to an external impact against said firstbeam.
 9. A bumper system according to claim 3, wherein said other ofsaid first and second beams has a hollow tubular cross section defininga C-shape which opens horizontally toward said one beam.
 10. A bumpersystem according to claim 1, wherein each of said first and second beamsare of high-strength steel and are roll formed from steel.
 11. A bumpersystem according to claim 1, wherein said first and second end parts arenested one within the other at said first connections.
 12. A bumpersystem according to claim 11, wherein said first connection is definedby a pair of vertically spaced, horizontally elongated welds connectingthe first end part to the respective second end part.
 13. A bumpersystem according to claim 12, wherein each of said second fulcrum-likeconnections is defined by a generally vertically elongate weld betweensaid second beam and a respective said mounting part of said vehicle.14. A bumper system according to claim 1, wherein the center beam partis spaced forwardly from, and is free of direct connection with, saidcenter beam portion.
 15. A bumper system according to claim 1, whereinsaid first beam has a C-shaped cross section defining a recess whichopens rearwardly toward said second beam, said second beam having ahollow tubular cross section sized to at least partially nest withinsaid recess, and said second end parts being nested into the recessdefined in said first end parts at said connecting structures.
 16. Avehicle bumper system comprising: an elongate monolithic one-piece outerbumper beam having an upright front wall joined between rearwardlyprojecting top and bottom walls; an elongate one-piece inner bumper beampositioned adjacent but inwardly of said outer bumper beam, said innerbumper beam being joined at opposite ends thereof to respective oppositeend parts of said outer bumper beam by end connections which permit atleast limited force moment-induced, energy-absorbing flexing betweenadjacent end portions of said outer and inner beams, said endconnections being positioned substantially symmetrically on oppositesides of a centerplane of said bumper system; said inner beam beingconnected to a vehicle solely at two connecting points which arepositioned on opposite sides of said centerplane and are each spacedinwardly from a respectively adjacent said end connection, said outerbeam being free of direct connection to said vehicle; said outer beambeing of a preshaped horizontally bowed configuration so that anelongate center beam section thereof is bowed outwardly and isphysically spaced from a center beam part of said inner beam whichextends between said connecting points; and said outer beam, whensubjected to an inward impact, effecting transfer of impact forces alongthe outer beam to the end connections to cause the center beam part ofthe inner beam to bow outwardly toward the outer beam.
 17. A vehiclebumper system according to claim 16, wherein one of said beams comprisesa hollow tube having a generally rectangular cross section, wherein theother of said beams includes a cross section which at least in part isC-shaped and sized to permit at least partial front-to-back nesting withsaid one beam, and wherein end parts of the outer and inner beams arenested one within the other at said end connections.
 18. A vehiclebumper system according to claim 17, wherein the inner beam includes apair of cantilevered end beam parts which each extend from oneconnecting point to the adjacent end connection, said end beam partselastically deflecting inward about the respective connecting point asthe center beam part bows outwardly in response to imposition of anexternal impact against said outer beam.
 19. A vehicle bumper systemaccording to claim 16, wherein each of said beams comprises a one-pieceroll formed steel member, and each of said beams has a yield strength ofat least 100 ksi.
 20. A vehicle bumper system according to claim 19,wherein a deformable energy-absorbing communication member is connectedbetween said center beam portion and said center beam part to permitlimited direct energy transfer therethrough upon external impact againstsaid outer beam, and/or a blocking member is mounted on one of saidcenter beam portion and said center beam part and is positioned forblocking engagement with the other of said center beam portion and saidcenter beam part as they move toward one another.
 21. A vehicle bumpersystem according to claim 18, wherein said outer beam is C-shaped anddefines an elongate recess which opens rearwardly toward said innerbeam; wherein said inner beam comprises said hollow tube which is sizedsuch that the end beam parts thereof are nested within said recess; andwherein said outer beam is preshaped into a horizontal arc-shapedconfiguration so that the center beam section is bowed horizontallyoutwardly away from said inner beam and is maintained in a generallynon-deflected condition when assembled with said inner beam.
 22. Avehicle bumper system according to claim 21, wherein each of said outerand inner beams is of substantially uniform cross section throughout thelengthwise extent thereof.
 23. A vehicle bumper system according toclaim 21, wherein each said first fulcrum-like connection is defined bya weld between said inner and outer beams.
 24. A vehicle bumper systemaccording to claim 21, wherein each said second fulcrum-like connectionis defined by a weld between said inner beam and said vehicle mountingpart.
 25. A vehicle bumper system according to claim 24, wherein eachsaid first fulcrum-like connection is defined by a weld between saidinner and outer beams.
 26. A bumper system for attachment to an end of avehicle, comprising: a first horizontally elongate beam positioned toextend transversely relative to a traveling direction of the vehicle; asecond horizontally elongate beam positioned adjacent but inwardly ofsaid first beam and extending transversely relative to said travelingdirection; said first beam being of substantially uniform cross sectionthroughout the length thereof and having an elongate center beam partwhich extends between and joins to a pair of first end parts as definedadjacent opposite ends of said first beam, said second beam being ofsubstantially uniform cross section throughout the length thereof andhaving second end parts adjacent opposite free ends thereof, said secondend parts being disposed adjacent said first end parts respectively; aconnecting structure joining each said first end part to the adjacentsecond end part, said connecting structures defining a pair of firstenergy-absorbing fulcrum-like connections between said first and secondbeams adjacent opposite ends thereof; each of said first and secondbeams being of high strength steel and being substantially nonstressedwhen joined together by said connecting structures; said second beambeing joined to mounting parts of said vehicle by a pair of sidewardlyspaced connection structures which define a pair of secondenergy-absorbing fulcrum-like connections between said vehicle and saidsecond beam, said second fulcrum-like connections being spaced inwardlyfrom said first fulcrum-like connections so that said second beamincludes an elongate center beam portion which extends between saidsecond fulcrum-like connections and a pair of end beam portions whicheach extends from one of said second fulcrum-like connections to theadjacent first fulcrum-like connection; said first beam beingpermanently preshaped so that said center beam part is bowedhorizontally forwardly from said first end parts so as to be spacedforwardly from but generally horizontally aligned with the center beamportion of said second beam; said first beam having at least ahorizontally oriented C-shaped cross section defining a recess whichextends lengthwise of said first beam and opens rearwardly toward saidsecond beam; said second beam being tubular in cross section and ofsmaller vertical height than said first beam so that the second endparts of said second beam where they join to said connecting structuresare nested in said recess of said first beam; whereby an external impactagainst said first beam transmits force to said pair of firstfulcrum-like connections to effect elastic deflection of said end beamportions and forward bowing of said center beam portion of said secondbeam.
 27. A bumper system according to claim 26, wherein said first beamincludes rearwardly cantilevered upper and lower legs which verticallystraddle said recess, and each of said legs being defined by a hollowchannel structure which is closed at the rear free end thereof.
 28. Abumper system according to claim 27, wherein at least one of said firstand second fulcrum-like connections is defined by an elongate line-likewelded connection with said inner beam.
 29. A bumper system according toclaim 28, wherein the center beam part and the center beam portion areinitially free of direct rigid connection therebetween to permitrelative movement therebetween in response to external impact on saidfirst beam; and wherein a deformable energizing member is connecteddirectly between the center beam part of said first beam and the centerbeam portion of said second beam to permit partial energy absorption andpartial transference of force to the center beam portion of said secondbeam upon imposition of an external impact against said first beam.